This invention relates to a recording medium for a reproducing or a recording and reproducing of an optical information.
Recent years, there has been given a great attention to an optical information recording medium wherein such information as voice and image are recorded as variation in shape, dimension and the like of pit (or concave) or block (or convex) and then optically read out to reproduce such voice, image and the like. There have already been put to practical use a variety of recording media, for example, an optical disc to be used for reproducing only, an optical disc capable of directly writing and directly reading, the so-called DRAW (i.e., Direct Read After Write) and so on, and they have been widely utilized for various purposes of document filing, image filing, audio system or computer memory.
Such a recording medium should be frequently received in a container, in order to prevent it from adhesion of dust, prevent it from adhesion of stains by direct touch with fingers of any persons dealing with it or simplify its handling. As the container, there have been known various forms depending upon the purposes of their utility, for example, for a cartridge-type, a jacket-type or a jukebox-type. From the functional point of view, there have been proposed, for instance, a container which is so constructed as to accomplish reproducing or recording with a recording medium as received or a container wherein a recording medium is drawn out and then reproducing or recording may be accomplished. The recording medium, unless being reproduced or recorded, should be stored in such container.
Although, a recording medium should be prepared under an extremely clean environment, fungi such as mold and the like may adhere to the recording medium, or fungi such as mold may be considerably present in the place where the recording medium is to be handled, e.g., in an office space or indoors at common houses and such fungi may adhere to recording media or containers, whereby mold may propagate under ordinary environmental conditions where the recording media is stored. Consequently, there have been presented problems of various harmful effects caused by mold. For example, if any mold propagates over a transparent base panel of the recording medium, through which a reproducing light or a recording light may pass, said reproducing or recording light could not sufficiently irradiate the recording medium because of the effect of the mold and there have been posed those problems of a lowered CN ratio, a generated sensitivity irregurality, an increased error rate and others. Moreover, if any mold grows in the recording medium, there have been problems of variation in absorbance or reflectance of the recording medium or variation in physical properties such as heat conductivity or hardness to bring reduction in sensitivity or varied shape of pits or blocks. If an adhesive is employed for constituting the record medium, propagation of molds on the adhesive would cause a lowered adhesivity and then a reduced mechanical durability. If any molds propagate on the container for the recording medium, there have been the following problems; when a mold may grow on an outer frame, a dealing person may be subjected to molds and further a record-reproducing apparatus may be sustained with molds to damage environmental hygiene. When a mold may grow at a movable part in a jukebox-type container, movement of said movable parts would be disturbed and the container would be out of order. When a mold may grow on a sealing material in the container with a sealed structure, said sealing material would be denatured and said sealed structure would be broken. In the case where the container is to be constructed with an adhesive, if a mold may grow in said adhesive, adhesivity would be decreased to break the container. Further, the mold grown in the container would transfer to the recording medium which is put in the container, thereby presenting the above-mentioned problems.